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Aerial Archaeology

Since the 1990s the institute of Archaeological Studies provides a laboratory for aerial archaeology equipped with extensive features of modern technology. Its research and educational capabilities are available in many areas.

Circular enclosure in a maize field
Fig. 01: Circular enclosure in a maize field, taken 28th August 2012
© aerial image: B. Song

Archaeological interpretation of aerial images

Primarily it deals with the archaeological interpretation of aerial images which have not been taken for archaeological purposes. Generally it concerns itself with the following aspects: the research of existing external images, the purchase of ideal archaeological images, the archiving of acquired images and the archaeological interpretation of them.

In aerial archaeology a number of various sources of information are exploited. Among those are e.g. the archives of military reconnaissance, geological and geographical remote sensing, land surveying etc. On the basis of aerial image catalogues and indicators aerial images are – depending on the objectives – selected and tentatively viewed. Among others, the criteria for selection are image types (vertical or angled images, image overlapping), image scale and recording time (time of year and time of day). The selected aerial images are obtained either by loan or purchase. Later these images are archived and prepared for interpretation. Depending on the aim and individual requirement the actual interpretation can be divided into different working phases, such as the preliminary interpretation, interpretation, the verification by fieldwork etc. The contents of archaeological aerial images are recognized, interpreted and depending on the aim in a variety of ways (preferably notationally and cartographically) documented.

Archaeological Aerophotogrammetry

At the institute of Archaeological Studies the Aerophotogrammetry is realised on a digital basis. Both the mapping photographs (survey purpose of vertical aerial images) and the aerial images of the airborne prospection (usually angled images) can be rectified or alternatively georeferenced. The main reason for the geometric image rectification is to correct the aberrations which occur due to the central projection of the aerial images. After the graphic rectification aerial images with certain map properties can be gained. Therefore these rectified aerial images can be further processed to aerial maps with less effort. Furthermore aerial images can be projected into a geographic coordinate system or into a coordinate system of the national survey (georeferenced). This can serve as the basis for an archaeological information system.

Alpen-Drupt: Roman military encampment visible as crop marks
Fig. 02: Alpen-Drupt: Roman military encampment visible as crop marks, taken 18th June 2013.
© aerial image: B. Song

Aerial Archaeology

This flexibility allows the recording and exploration of archaeological sites that would usually only be discovered by accident and could only be surveyed otherwise with great effort.
The aerial archaeology is a method of discovery, observation and documentation for archaeological sites. While the archaeological aerial image interpretation is mainly used for field surveys of overground preserved sites it also can be used on completely levelled terrain and to find underground preserved sites. The aerial survey specifically is the direct overfly of important archaeological areas. Usually a two- or four-seated sporting aircraft like a Cessna 150 or the Cessna 172 is used. If a new site is discovered it will be charted and subsequently - via a digital camera GPS- geolocated. The combination of a small aeroplane with an easy to operate camera system allows an observation and documentation of the sites through different perspectives and flight levels at any time of the year. Through that it is possible to document and investigate archaeological sites which are usually discovered by accident.

Archaeological Cartography

Sites with different archaeological features can be recorded cartographically in form of grid-based digital aerial maps and vector-based line drawn maps. This option is important for regions and countries in which topographical maps are either missing or unavailable. At the institute numerous aerial maps with different scales and an atlas based on the archaeological information system were created.

Schermbeck-Damm, double-trenches of a motte-and-bailey castle visible as positive snow marks
Fig. 03: Schermbeck-Damm, double-trenches of a motte-and-bailey castle visible as positive snow marks, taken on 14th December 2012.
© aerial image: B. Song

Archaeological information systems

Archaeological information usually consist of spatial data. The best option to systematically record, evaluate and utilise the data is by using the Geographic Information System (GIS). The GIS consists of a system of computer software, hardware, data and personnel by which spatial data can be processed, analysed and presented. Currently the institute uses ArcGIS (campus licence). For the purposes of several archaeological research projects GIS proved to be a useful tool in the cultural heritage administration and in the archaeological studies. The institute has extensive theoretical and practical experiences with the GIS.